Communications and effective system control are still big challenges unmanned aircraft developers are facing if they want unfettered access to US airspace.

Those were just a couple of the conclusions described in a recent Government Accountability Office report on the status of unmanned aircraft and the national airspace. The bottom line for now seems to be that while research and development efforts are under way to mitigate obstacles to safe and routine integration of unmanned aircraft into the national airspace, these efforts cannot be completed and validated without safety, reliability, and performance standards, which have not yet been developed because of data limitations, the GAO concluded.

The GAO report noted that current domestic uses of drones are limited to activities such as law enforcement, forensic photography, border security, and scientific data collection. According to an industry forecast, the market for unmanned aircraft could be worth $89 billion with the associated research and development for production estimated to be $28.5 billion over the next 10 years.

The main issues include the ability for drones to avoid other aircraft in the sky; what backup network is available and how should the machine behave if it loses its communications link and other network issues.

From the GAO report:

Avoidance: To date, no suitable technology has been deployed that would provide UAS with the capability to sense and avoid other aircraft and airborne objects and to comply completely with FAA regulatory requirements of the national airspace. However, research and development efforts by FAA, DOD, NASA, and MITRE, among others, suggests that potential solutions to the sense and avoid obstacle may be available in the near term. The Department of the Army is working on a ground-based sense and avoid system that will detect other airborne objects and allow the pilot to direct the drone to maneuver to a safe location. The Army has successfully tested one such system, but it may not be useable on all types of drones, the GAO stated

Control: Ensuring uninterrupted command and control for both small and large UAS remains a key obstacle for safe and routine integration into the national airspace. Since unmanned aircraft fly based on pre-programmed flight paths and by commands from a pilot-operated ground control station, the ability to maintain the integrity of command and control signals are critically important to ensure that the drone operates as expected and as intended, the GAO said

Lost links: In a "lost link" scenario, the command and control link between the UAS and the ground control station is broken because of either environmental or technological issues, which could lead to loss of control of the drone. To address this type of situation, unmanned aircraft generally have pre-programmed maneuvers that may direct the machine to hover or circle in the airspace for a certain period of time to reestablish its radio link. If the link is not reestablished, then the drone will return to "home" or the location from which it was launched, or execute an intentional flight termination at its current location. FAA and MITRE have been measuring the impacts of lost link on national airspace safety and efficiency, but the standardization of lost link procedures, for both small and large unmanned aircraft, has not been finalized. Currently, according to FAA, each Certificates of Waiver or Authorization [permission to fly certain drones in specific public airspace ] has a specific lost link procedure unique to that particular operation and air traffic controllers should have a copy for reference at all times. Until procedures for a lost link scenario have been standardized across all types of UAS, air traffic controllers must rely on the lost link procedures established in each COA to know what a particular UAS will do in such a scenario, the GAO stated.

Network security: The jamming of the GPS signal being transmitted to the UAS could also interrupt the command and control of drone operations. In a GPS jamming scenario, the aircraft could potentially lose its ability to determine its location, altitude, and the direction in which it is traveling. Low cost devices that jam GPS signals are prevalent. According to one industry expert, GPS jamming would become a larger problem if GPS is the only method for navigating a UAS. This problem can be mitigated by having a second or redundant navigation system onboard the aircraft that is not reliant on GPS, which is the case with larger drones typically operated by DOD and DHS. Encrypting civil GPS signals could make it more difficult to "spoof" or counterfeit a GPS signal that could interfere with the drone navigation. Non-military GPS signals, unlike military GPS signals, are not encrypted and transparency and predictability make them vulnerable to being counterfeited, or spoofed., the GAO report stated.

Radio spectrum: Progress has been made in obtaining additional dedicated radio-frequency spectrum for drone operations, but additional dedicated spectrum, including satellite spectrum, is still needed to ensure secure and continuous communications for both small and large drone operations. The lack of protected radio-frequency spectrum for unmanned operations heightens the possibility that a pilot could lose command and control of an aircraft. Unlike manned aircraft-which use dedicated, protected radio frequencies-UAS currently use unprotected radio spectrum and, like any other wireless technology, remain vulnerable to unintentional or intentional interference. This remains a key security and safety vulnerability because, in contrast to a manned aircraft in which the pilot has direct physical control of the aircraft, interruption of radio transmissions can sever the drone's only means of control, the GAO said.

Test ranges: FAA has taken steps to develop, but has not yet established, a program to integrate UAS at six test ranges, as required by the 2012 Act. As part of these ranges, FAA must safely designate airspace for integrated manned and unmanned flight operations, develop certification standards and air traffic requirements for drones, ensure the program is coordinated with NextGen[the FAA's future air traffic control system], and verify the safety of unmanned aircraft and related navigation procedures before integrating them into the national airspace. FAA expects data obtained from these test ranges will contribute to the continued development of standards for the safe and routine integration of drones.

Cooney is an Online News Editor and the author of the Layer 8 blog, Network World's daily home for the not-just-networking news. He has been working with Network World since 1992. You can reach him at mcooney@nww.com.